This application relates to medical diagnosis and treatment of tissue with instruments, specifically locating a tissue structure and positioning an instrument relative to that tissue structure.
Tissue biopsy is an example of treating tissue with medical instruments. One method of performing a biopsy on a suspicious structure in tissue is for a clinician to first palpate the tissue to locate the structure. Upon locating the structure, the clinician uses her fingers to constrain the structure. Once the clinician has done so, the clinician inserts the biopsy needle into the tissue to the approximate depth of the structure. As the needle penetrates the outside portion of the mass, the clinician senses a slight increase in resistance against the needle, which confirms that the needle has reached the structure. Because the clinician does not know for certain the depth of the structure, obtaining a good sample of the tissue or the fluid in the structure typically involves some trial and error. The clinician may insert and reinsert the needle multiple times to ensure that a good sample has been obtained.
Other biopsy methods include stereotactic X-ray imaging, in which two X-ray images at different angles are taken from tissue. The stereotactic image is then used to locate the structure from which the biopsy is to be taken. Ultrasound imaging has also been used to guide the biopsy needle.